The present invention relates to telescoping slide assemblies for moving equipment between a fully retracted position and an extended position, and particularly to a slide assembly having at least three slide members and lock mechanisms for locking the slide members in various retracted and extended positions. More particularly, the present invention relates to a telescoping slide assembly that contains mechanisms for controlling unlocking of the slide members during telescoping movement of the slide members between extended and retracted positions.
A conventional telescoping slide assembly typically includes a stationary slide member, a load-carrying slide member, and an intermediate slide member. The intermediate slide member is positioned and configured to move the load-carrying slide member toward and away from the stationary slide member. Typically, a pair of telescoping slide assemblies are positioned in side-by-side spaced-apart parallel relation so that either a load-carrying platform or one or more pieces of equipment can be carried on the two side-by-side load-carrying slide members. It is also common to use a pair of telescoping slide assemblies to support a cabinet drawer between a retracted position inside the cabinet and an extended position outside the cabinet.
The stationary slide member is typically mounted to a fixed frame to anchor the slide assembly. The frame could be a cabinet, a truck bed, or any other suitable platform. For example, it is known to use telescoping slide assemblies to slide heavy pieces of equipment into and out of a truck bed.
Various kinds of equipment or loads can be anchored to the movable load-carrying slide members so that such loads can be moved easily relative to the truck bed or the like during telescoping extension and retraction of the intermediate and load-carrying slide members in each slide assembly relative to the stationary slide members that are anchored to the truck bed. Typically, a telescoping slide assembly is extended and retracted manually by an operator and thus must be capable of moving heavy loads easily and quickly under the control of an operator during loading of equipment onto the truck and unloading of equipment from the truck.
It is known to provide locking interconnections between each of the three slide members so that extension or retraction of the slide members relative to each other can be prevented. This allows a drawer or equipment rack mounted on a pair of telescoping slide assemblies to be extended outward in the extending direction and locked to maintain a desired extended position. Since these locking interconnections must generally be manually engaged and disengaged, separate manual unlocking actions are required before such a drawer or equipment can be extended. The use of a locking mechanism to prevent relative movement of two sliding tracks until manual release of the locking mechanism is known. See, for example, U.S. Pat. No. 4,200,352 to Fall et al.
Typically, as the telescoping slide assemblies extend to move the equipment or load from the retracted position, the slide members lock automatically in a partly extended position. An operator initiates the extension process by actuating a release mechanism to allow the slide members to extend relative to one another. When the intermediate slide member reaches its fully extended position, the load-carrying slide member automatically locks to the intermediate slide member and thereby stops the slide assembly in a partly extended position. In order to continue moving the load to the fully extended position, the operator must actuate the release mechanism a second time to allow the load-carrying slide member to extend to its fully extended position relative to the intermediate slide member. In many applications, the need for a second actuation of the release mechanism is a nuisance. Therefore, telescoping slide assemblies that provide a mechanism for allowing the slide members to fully extend without stopping at a partly extended position would be an improvement over conventional slide assemblies.
Another problem facing some users of telescoping slide assemblies is accidental unlocking of the telescoping slide assemblies. In mobile situations, where the drawers or equipment racks are mounted in a vehicle such as a truck, the slide assemblies are susceptible to inadvertent release during turns or acceleration of the vehicle. For instance, where the slide assemblies are mounted in a truck to support a heavy piece of equipment, the centrifugal force of the heavy equipment accelerating in the turn causes the slide assemblies to overcome the locking mechanism, thereby allowing the slide assemblies to extend. An unexpected extension of the slide assemblies can be especially troublesome when the slide assemblies are supporting heavy equipment or expensive equipment. Therefore, telescoping slide assemblies that incorporate a mechanism to prevent the inadvertent extension of the assemblies during turns or acceleration would provide a substantial improvement over conventional slide assemblies.
According to the present invention, a telescoping slide assembly is provided for moving a load between a fully retracted position and a fully extended position. The telescoping slide assembly includes a load-carrying slide member, an intermediate slide member, and a stationary slide member. The telescoping slide assembly further includes a mechanism for locking the load-carrying slide member relative to the stationary slide member when the assembly is in the fully retracted position. The telescoping slide assembly further includes means for preventing the assembly from locking at a partly extended position during movement between the fully retracted position and the fully extended position.
In preferred embodiments, a locking lever is provided to lock the telescoping slide assembly in the fully retracted position. The locking lever is pivotably coupled to the load-carrying slide member and is positioned to engage locking apertures that are formed in the intermediate and stationary slide members. The locking apertures in the intermediate and stationary slide members are in registry when the slide assembly is in the fully retracted position so that a lip formed on the locking lever can engage a complementary lip formed on the aperture in the stationary slide member. When the lips are engaged, they overlap each other, and the locking lever locks the load-carrying and stationary slide members in the fully retracted position.
The overlap of the lips serves another purpose in addition to locking the slide assembly in the fully retracted position. When a force is applied to the fully retracted slide assembly of such an angle and magnitude that would tend to extend the slide members, the overlap provides a mechanism for maintaining the locking lever in engagement with the locking apertures and preventing inadvertent release of the locking lever, such as might occur during turns or acceleration. Thus, all extending forces must be removed from the telescoping slide assembly in order to release the locking lever and unlock the slide assembly from the fully retracted position, thereby eliminating inadvertent extension of the telescoping slide assembly.
The locking lever is also formed to include a shoulder for locking the load-carrying slide member in its fully extended position relative to the intermediate slide member. The shoulder is sized to fit in a notch formed in the intermediate slide member. The shoulder is positioned to engage the notch when the load-carrying slide member is in its fully extended position relative to the intermediate slide member. It is not necessary that the intermediate slide member be fully extended for the shoulder to engage the notch.
The locking lever is also configured so that it does not automatically establish a locking connection between the load-carrying and intermediate slide member when the intermediate slide member reaches a partly extended position. While the locking lever is engaged with the locking aperture in the stationary slide member in the fully retracted position, the locking lever is also positioned in the locking aperture in the intermediate slide member and blocks the intermediate slide member from moving relative to the stationary slide member. When the locking lever is disengaged from the stationary slide member and the slide assembly is allowed to extend from the fully retracted position, a lifting ramp appended to the locking lever operates to cam the locking lever out of engagement with the locking apertures in the intermediate and stationary slide members. By camming the locking lever out of engagement with the aperture in the intermediate slide member, the lifting ramp prevents the load-carrying slide member from locking to the intermediate slide member during extension at a partly extended position during movement of the load-carrying slide member toward an extended position.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.